Apolipoprotein E polymorphism modifies the alcohol-HDL association observed in the National Heart, Lung, and Blood Institute Family Heart Study

Quantile-Dependent Expressivity and Gene-Lifestyle Interactions Involving High-Density Lipoprotein Cholesterol

BACKGROUND

The phenotypic expression of a high-density lipoprotein (HDL) genetic risk score has been shown to depend upon whether the phenotype (HDL-cholesterol) is high or low relative to its distribution in the population (quantile-dependent expressivity). This may be due to the effects of genetic mutations on HDL-metabolism being concentration dependent.

METHOD

The purpose of this article is to assess whether some previously reported HDL gene-lifestyle interactions could potentially be attributable to quantile-dependent expressivity.

SUMMARY

Seventy-three published examples of HDL gene-lifestyle interactions were interpreted from the perspective of quantile-dependent expressivity. These included interactive effects of diet, alcohol, physical activity, adiposity, and smoking with genetic variants associated with the ABCA1, ADH3, ANGPTL4, APOA1, APOA4, APOA5, APOC3, APOE, CETP, CLASP1, CYP7A1, GALNT2, LDLR, LHX1, LIPC, LIPG, LPL, MVK-MMAB, PLTP, PON1, PPARα, SIRT1, SNTA1,and UCP1genes. The selected examples showed larger genetic effect sizes for lifestyle conditions associated with higher vis-à-vis lower average HDL-cholesterol concentrations. This suggests these reported interactions could be the result of selecting subjects for conditions that differentiate high from low HDL-cholesterol (e.g., lean vs. overweight, active vs. sedentary, high-fat vs. high-carbohydrate diets, alcohol drinkers vs. abstainers, nonsmokers vs. smokers) producing larger versus smaller genetic effect sizes. Key Message: Quantile-dependent expressivity provides a potential explanation for some reported gene-lifestyle interactions for HDL-cholesterol. Although overall genetic heritability appears to be quantile specific, this may vary by genetic variant and environmental exposure.

Analysis of apolipoprotein E genetic polymorphism in a large ethnic Hakka population in southern China

There is currently no data about the genetic variations of APOE in Hakka population in China. The aim of this study was to analyze the allelic and genotypic frequencies of APOE gene polymorphisms in a large ethnic Hakka population in southern China. The APOE genes of 6,907 subjects were genotyped by the gene chip platform. The allele and genotype frequencies were analyzed. Results showed that the ∊3 allele had the greatest frequency (0.804) followed by ∊2 (0.102), and ∊4 (0.094), while genotype ∊3/∊3 accounted for 65.43% followed by ∊2/∊3 (15.85%), ∊3/∊4 (14.13%), ∊2/∊4 (3.01%), ∊4/∊4 (0.84%), and ∊2/∊2 (0.74%) in all subjects. The frequencies of the ∊4 allele in Chinese populations were lower than Mongolian and Javanese, while the frequencies of the ∊2 allele were higher and ∊4 allele lower than Japanese, Koreans, and Iranian compared with the geographically neighboring countries. The frequencies of ∊2 and ∊4 alleles in Hakka population were similar to the Vietnamese, Chinese-Shanghai, Chinese-Kunming Han and Chinese-Northeast, and French. The frequency of ∊2 in Hakka population was higher than Chinese-Dehong Dai and Chinese-Jinangsu Han. The low frequency of the APOE ∊4 allele may suggest a low genetic risk of Hakka population for cardiovascular disease, Alzheimer's disease, and other diseases.

Apolipoprotein E genotyping and questionnaire-based assessment of lifestyle risk factors in dyslipidemic patients with a family history of Alzheimer's disease: test development for clinical application

The cholesterol-raising properties of the apolipoprotein E (APOE) epsilon-4 (ε-4) allele has been validated in the South African population. Mounting evidence supports the added value of APOE genotyping for the evaluation of cardiovascular risk in dyslipidemic patients beyond its established role in the diagnosis of late-onset Alzheimer's disease (AD). The aim of this study was to determine the potential benefits of combining AD family history with questionnaire-based lifestyle assessment to facilitate the clinical interpretation of APOE genotyping results. A total of 580 unrelated South African individuals prospectively enrolled in a chronic disease screening program incorporating a genetic component (2010-2015) was selected for inclusion in this study based on the presence (75) or absence (505) of AD family history. Biochemical assessment of their lipid profiles was performed according to standard laboratory protocols. All study participants were genotyped for the APOE ε-2/ε-3/ε-4 alleles using allele-specific TaqMan real-time polymerase chain reaction technology. In patients without a family history of AD, APOE genotype modified the relationship between alcohol intake and body mass index (p = 0.026), with a significant positive correlation noted between these parameters being limited to ε-4 allele carriers. APOE genotype also modified the association between alcohol intake and total serum cholesterol in patients with a positive family history of AD (p = 0.026). We demonstrated the benefits of a questionnaire-based approach for assessment of lifestyle risk factors to facilitate clinical interpretation of APOE genotyping results for targeted intervention in a genetic subgroup of dyslipidemic patients at increased risk for AD.

Genomic medicine and risk prediction across the disease spectrum

Genomic medicine is based on the knowledge that virtually every medical condition, disease susceptibility or response to treatment is caused, regulated or influenced by genes. Genetic testing may therefore add value across the disease spectrum, ranging from single-gene disorders with a Mendelian inheritance pattern to complex multi-factorial diseases. The critical factors for genomic risk prediction are to determine: (1) where the genomic footprint of a particular susceptibility or dysfunction resides within this continuum, and (2) to what extent the genetic determinants are modified by environmental exposures. Regarding the small subset of highly penetrant monogenic disorders, a positive family history and early disease onset are mostly sufficient to determine the appropriateness of genetic testing in the index case and to inform pre-symptomatic diagnosis in at-risk family members. In more prevalent polygenic non-communicable diseases (NCDs), the use of appropriate eligibility criteria is required to ensure a balance between benefit and risk. An additional screening step may therefore be necessary to identify individuals most likely to benefit from genetic testing. This need provided the stimulus for the development of a pathology-supported genetic testing (PSGT) service as a new model for the translational implementation of genomic medicine in clinical practice. PSGT is linked to the establishment of a research database proven to be an invaluable resource for the validation of novel and previously described gene-disease associations replicated in the South African population for a broad range of NCDs associated with increased cardio-metabolic risk. The clinical importance of inquiry concerning family history in determining eligibility for personalized genotyping was supported beyond its current limited role in diagnosing or screening for monogenic subtypes of NCDs. With the recent introduction of advanced microarray-based breast cancer subtyping, genetic testing has extended beyond the genome of the host to also include tumor gene expression profiling for chemotherapy selection. The decreasing cost of next generation sequencing over recent years, together with improvement of both laboratory and computational protocols, enables the mapping of rare genetic disorders and discovery of shared genetic risk factors as novel therapeutic targets across diagnostic boundaries. This article reviews the challenges, successes, increasing inter-disciplinary integration and evolving strategies for extending PSGT towards exome and whole genome sequencing (WGS) within a dynamic framework. Specific points of overlap are highlighted between the application of PSGT and exome or WGS, as the next logical step in genetically uncharacterized patients for whom a particular disease pattern and/or therapeutic failure are not adequately accounted for during the PSGT pre-screen. Discrepancies between different next generation sequencing platforms and low concordance among variant-calling pipelines caution against offering exome or WGS as a stand-alone diagnostic approach. The public reference human genome sequence (hg19) contains minor alleles at more than 1 million loci and variant calling using an advanced major allele reference genome sequence is crucial to ensure data integrity. Understanding that genomic risk prediction is not deterministic but rather probabilistic provides the opportunity for disease prevention and targeted treatment in a way that is unique to each individual patient.

Effects of ethanol intake on lipoproteins

These review discusses the effects of ethanol on lipoprotein levels and function as related to atherosclerosis and cardiovascular disease (CVD), with special emphasis on recent publications. Ethanol's effects on high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides (TG), and other CVD risk factors recently have been explored. Other new data address genetic and demographic predictors and mechanisms of these responses. Not surprisingly, the results of some recent studies corroborate, whereas others differ from, earlier seemingly well-established findings. Prior and recent evidence shows favorable changes in HDL, other CVD risk factors, and CVD event rates with moderate, regular ethanol intake, and recent publications have explored the mechanisms of this relationship. Application of these findings in clinical practice remains problematic, however, due to the lack of randomized, controlled clinical trials of ethanol and due to the potential hazards of ethanol consumption.

A case-control study on the effects of the apolipoprotein E genotypes in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has reached epidemic proportions being the most common cause of chronic liver disease in Western countries. The Apolipoprotein E (ApoE) gene has three major isoforms encoded by the ε2, ε3, and ε4 alleles, with the ε4 allele associated with hypercholesterolemia and the ε2 allele with the opposite effect. The role of apoE genotypes on NAFLD has been previously investigated with conflicting results. Our hospital-based case-control study conducted in Italy aims to explore the effect of the apoE genotypes on NAFLD risk and their effect on the clinical features of NAFLD patients. 310 NAFLD cases and 422 controls were genotyped for apoE. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) from logistic regression were used to explore the relationship between NAFLD and apoE genotypes, as well as their interaction with selected demographic and lifestyle factors. ApoE ε4 allele carriers showed a statistically significant two-fold reduction of NAFLD risk (OR = 0.51, 95% CI: 0.28-0.93) compared with ε3 homozygotes. A statistically significant lower HDL cholesterol level was observed for ApoE ε4 carriers if compared with ε3/ε3 genotype or ApoE ε2 carriers with a nearly linear decreasing trend from ApoE ε2 to ApoE ε4 carriers. Our study reports for the first time a protective effect of the ε4 allele towards NAFLD that might be attributable to its role in the regulation of hepatic triglycerides rich very low-density lipoproteins secretion.

Alcohol intake

Alcohol consumption and its association with health or illness states are of great interest from the nutritional genomics point of view. This interest is centered not only on investigating the genetic variants that can modulate the effects of alcoholic beverages on different intermediate and final disease phenotypes (mainly cardiovascular diseases and cancer), but also on finding out how the genome influences the amount of alcohol consumed and consumption habits. This chapter reviews the latest findings on alcohol consumption trends, the methodological limitations in the analysis of alcohol consumption, and the main genes and polymorphisms related to alcohol intake, including the inconsistent results from genome-wide association studies (GWASs). It also reviews the effects of alcohol consumption on cardiovascular diseases and cancer and the studies analyzing the interactions between different genetic polymorphisms and alcohol in phenotypes related to these diseases, discussing the studies' advantages and limitations as well as future research perspectives.

Saturated fat intake and alcohol consumption modulate the association between the APOE polymorphism and risk of future coronary heart disease: a nested case-control study in the Spanish EPIC cohort

The association is still not clear between the common APOE polymorphism and coronary heart disease (CHD) risk, nor its modulation by diet. Thus, our aim was to study the association between the APOE genotypes and incident CHD and how dietary fat and alcohol consumption modify these effects. We performed a nested case-control study in the Spanish European Prospective Investigation into Cancer and Nutrition cohort. Healthy men and women (41,440, 30-69 years) were followed up over a 10-year period, with the incident CHD cases being identified. We analyzed 534 incident CHD cases and 1123 controls. APOE, dietary intake and plasma lipids were determined at baseline. The APOE polymorphism was significantly associated with low-density lipoprotein cholesterol (LDL-C), and gene-alcohol interactions in determining LDL-C were detected. In the whole population, the E2 allele was significantly associated with a lower CHD risk than E3/E3 subjects [odds ratio (OR), 0.58; 95% confidence interval (CI), 0.38-0.89]. The E4 allele did not reach statistical significance vs. E3/E3 (OR, 1.17; 95% CI, 0.88-1.58). However, saturated fat intake modified the effect of the APOE polymorphism in determining CHD risk. When saturated fat intake was low (<10% of energy), no statistically significant association between the APOE polymorphism and CHD risk was observed (P=.682). However, with higher intake (≥10%), the polymorphism was significant (P=.005), and the differences between E2 and E4 carriers were magnified (OR for E4 vs. E2, 3.33; 95% CI, 1.61-6.90). Alcohol consumption also modified the effect of the APOE on CHD risk. In conclusion, in this Mediterranean population, the E2 allele is associated with lower CHD risk, and this association is modulated by saturated fat and alcohol consumption.

Effects of ethanol intake on lipoproteins and atherosclerosis

PURPOSE OF REVIEW

This article reviews published studies regarding effects of ethanol intake on lipoprotein levels and function as they relate to atherosclerosis, with special emphasis on recent publications in the past 2 years.

RECENT FINDINGS

Some recent studies have explored novel mechanisms of ethanol on atherogenesis via effects on HDL composition and function. Other studies have focused on changes in levels of LDL cholesterol (LDL-C), triglyceride, and other factors such as inflammatory markers C-reactive protein (CRP) and lipoprotein-associated phospholipase A2 (LpPLA2). Other areas of emphasis have been the effects within specific populations and between genders, as well as contributions of genetic polymorphisms in prediction of response to ethanol. Surprisingly, results of recent studies are often at odds with prior, seemingly well established findings.

SUMMARY

The association between moderate ethanol consumption and favorable changes in lipoproteins and lipoprotein-related factors in atherosclerosis continues to become better established with the publication of new studies in this field. Continued progress is being achieved in understanding the well established link between moderate intake and reduced risk of cardiovascular disease (CVD). Nevertheless, it remains difficult to implement these findings in clinical practice due to the ongoing lack of randomized, blinded clinical trial data, and the well known hazards of excess ethanol consumption.

Apolipoprotein e, alcohol consumption, and risk of ischemic stroke: the Framingham Heart Study revisited

BACKGROUND

Data on the association between alcohol consumption and ischemic stroke have been inconsistent. It is not known whether allele epsilon(4) of the apolipoprotein E (apoE) gene modifies the alcohol-stroke association. We sought to examine whether epsilon(4) allele of the apoE gene influences the association between alcohol consumption and ischemic stroke or high-density lipoprotein (HDL) cholesterol.

METHODS

We examined a cohort of 7676 person-observations of the Framingham Heart Study. Incident stroke was ascertained by standardized methods. We used Cox proportional hazard model to estimate hazard ratios of ischemic stroke.

RESULTS

The average age at baseline was 63 years and 55% of the participants were women. During a mean follow-up of 7.4 years, 222 new cases of ischemic stroke occurred (56 embolic and 166 atherothrombotic events). Comparing current drinkers with nondrinkers, multivariable adjusted hazard ratio (95% confidence interval) for ischemic stroke was 0.50 (0.24-1.07) in the absence of epsilon(4) allele and 0.70 (0.24-2.05) in the presence of epsilon(4) allele (P for interaction = .64) for those younger than 65 years. Similarly, we did not observe a statistically significant interaction between epsilon(4) allele and alcohol consumption on the risk of stroke among people aged 65 years and older (P for interaction = .17). Alcohol consumption was positively associated with HDL cholesterol independent of epsilon(4) allele and age.

CONCLUSIONS

Our data do not provide evidence for an interaction between epsilon(4) allele and alcohol consumption on the risk of ischemic stroke in this population. Furthermore, apoE polymorphism did not influence the alcohol-HDL relation.

Analyses of interaction effect between apolipoprotein E polymorphism and alcohol use as well as cholesterol concentrations on spontaneous deep intracerebral hemorrhage in the Taiwan population

BACKGROUND

To determine the interaction effect between APOE polymorphism and lipid concentrations and alcohol use on spontaneous deep intracerebral hemorrhage (SDICH) risks.

METHODS

We enrolled 217 SDICH patients and 280 controls. Anthropometrics, personal history, and concentrations of total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-c), and triglyceride were collected. Genotyping was determined by PCR-based restriction and electrophoresis assay. Associations were tested adjusting for multiple covariables.

RESULTS

Compared with the commonest genotype epsilon 3 epsilon 3, epsilon 2 epsilon 3 was inversely associated with TC (p=0.023) and LDL-c concentrations (p=0.005) in women. No APOE-alcohol interaction effect on lipids concentration was found. However, in men, there was a marginal effect of interaction between alcohol and APOE genotype epsilon 2 epsilon 3 vs. epsilon 3 epsilon 3 on SDICH risks (p=0.003), which is independent of TC concentration. In the male non-alcohol group, SDICH proportion was lower in the subjects carrying APOE epsilon 2 epsilon 3 (27.6%) than in those with epsilon 3 epsilon 3 (41.1%). In contrast, in the male alcohol consumption group, APOE epsilon 2 epsilon 3 was associated with a higher SDICH rate (77.8%) compared to epsilon 3 epsilon 3 (58.0%).

CONCLUSIONS

Male subjects carrying genotype epsilon 2 epsilon 3 tend to have a higher SDICH risk than those who have epsilon 3 epsilon 3 when they have alcohol exposure, but may have more benefit from alcohol abstinence.

Nutrigenetics and personalised nutrition: how far have we progressed and are we likely to get there?

Nutrigenetics and personalised nutrition are components of the concept that in the future genotyping will be used as a means of defining dietary recommendations to suit the individual. Over the last two decades there has been an explosion of research in this area, with often conflicting findings reported in the literature. Reviews of the literature in the area of apoE genotype and cardiovascular health, apoA5 genotype and postprandial lipaemia and perilipin and adiposity are used to demonstrate the complexities of genotype–phenotype associations and the aetiology of apparent between-study inconsistencies in the significance and size of effects. Furthermore, genetic research currently often takes a very reductionist approach, examining the interactions between individual genotypes and individual disease biomarkers and how they are modified by isolated dietary components or foods. Each individual possesses potentially hundreds of ‘at-risk’ gene variants and consumes a highly-complex diet. In order for nutrigenetics to become a useful public health tool, there is a great need to use mathematical and bioinformatic tools to develop strategies to examine the combined impact of multiple gene variants on a range of health outcomes and establish how these associations can be modified using combined dietary strategies.

Association between apolipoprotein E polymorphism, lipids, and coronary artery disease in Tunisian type 2 diabetes

BACKGROUND

The relationship between apolipoprotein E (ApoE) polymorphism, fasting lipid parameters, and coronary artery disease (CAD) is controversial.

METHODS

We studied this relationship, for the first time, in Tunisian type 2 diabetic patients. The studied population comprised 157 type 2 diabetic patients (145 of them were not on any lipid-lowering drugs). Fasting lipids were measured by enzymatic methods and ApoE genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Our results showed that the alleles E2, E3, and E4 were found in 4%, 88%, and 8% of patients, respectively. In the total type 2 diabetic population, no association was found between ApoE polymorphism, lipid parameters, and CAD. However, the E4 allele was associated with elevated low-density lipoprotein cholesterol concentration and with CAD in type 2 diabetic men.

CONCLUSION

The effect of ApoE polymorphism on CAD is gender-dependent in the Tunisian type 2 diabetic population. ApoE 4 allele may enhance atherogenesis indirectly by a strong effect on low-density lipoprotein cholesterol.

Impact of apoE genotype on oxidative stress, inflammation and disease risk

Although in developing countries an apolipoprotein E4 (apoE4) genotype may offer an evolutionary advantage, as it has been shown to offer protection against certain infectious disease, in Westernised societies it is associated with increased morbidity and mortality, and represents a significant risk factor for cardiovascular disease, late-onset Alzheimer's disease and other chronic disorders. ApoE is an important modulator of many stages of lipoprotein metabolism and traditionally the increased risk was attributed to higher lipid levels in E4 carriers. However, more recent evidence demonstrates the multifunctional nature of the apoE protein and the fact that the impact of genotype on disease risk may be in large part due to an impact on oxidative status or the immunomodulatory/anti-inflammatory properties of apoE. An increasing number of studies in cell lines, targeted replacement rodents and human volunteers indicate higher oxidative stress and a more pro-inflammatory state associated with the epsilon4 allele. The impact of genotype on the antioxidant and immunomodulatory/anti-inflammatory properties of apoE is the focus of the current review. Furthermore, current information on the impact of environment (diet, exercise, smoking status, alcohol) on apoE genotype-phenotype associations are discussed with a view to identifying particular lifestyle strategies that could be adapted to counteract the 'at-risk' E4 genotype.

Alcohol consumption and lipoprotein subclasses in older adults

CONTEXT

Limited evidence suggests that alcohol intake may be associated with lipoprotein subclass distribution, which could mediate its relationship with coronary heart disease.

OBJECTIVES

The objective was to determine the relationship of alcohol intake with lipoprotein particle subclasses.

DESIGN, SETTING, AND PARTICIPANTS

The study included a cross-sectional analysis of 1850 participants of the Cardiovascular Health Study aged 65 yr and older and free of clinical cardiovascular disease.

MAIN OUTCOME MEASURE

Lipoprotein subclass distribution was measured with nuclear magnetic resonance spectroscopy, according to self-reported alcohol intake.

RESULTS

Alcohol intake was associated with total low-density lipoprotein (LDL) particles in a U-shaped manner. Consumers of one or more drinks per week had the highest number of large LDL particles, whereas consumers of 7-13 drinks per week had the lowest number of small LDL particles. Alcohol intake was strongly positively associated with large- and medium-sized high-density lipoprotein (HDL) particles but had an inverse relationship with concentrations of small HDL particles and small- and medium-sized very-low-density lipoprotein particles. Average particle sizes of all three lipoproteins were positively associated with alcohol intake. Associations were generally stronger among women than men but in similar directions. Beverage type did not consistently modify these findings.

CONCLUSIONS

Alcohol intake is associated with less total LDL particles, lower levels of small LDL, HDL, and very-low-density lipoprotein particles, and higher levels of large LDL and medium- and large-sized HDL particles in older adults free of prevalent clinical cardiovascular disease.

Genetic factors affecting HDL levels, structure, metabolism and function

PURPOSE OF REVIEW

HDL is a recognized negative risk factor for the cardiovascular diseases. Establishing the genetic determinants of HDL concentration and functions would add to the prediction of cardiovascular risk and point to the biochemical mechanisms underlying this risk. The present review focuses on various approaches to establish genetic determinants of the HDL concentration, structure and function.

RECENT FINDINGS

While many genes contribute to the HDL concentration and collectively account for half of the variability, polymorphism of individual candidate genes contributes little. There are strong interactions between environmental and genetic influences. Recent findings have confirmed that APOA1 and ABCA1 exert the strongest influence on HDL concentrations and risk of atherosclerosis. CETP and lipases also affect the HDL concentration and functionality, but their connection to the atherosclerosis risk is conditional on the interaction between environmental and genetic factors.

SUMMARY

Analysis of genetic determinants of HDL-cholesterol in patients with specific disease states or in response to the environmental condition may be a more accurate way to assess variations in HDL concentration. This may result in defining the rules of interaction between genetic and environmental factors and lead to understanding the mechanisms responsible for the variations in HDL concentration and functionality.

Gene-alcohol interactions in the metabolic syndrome

AIMS

Recent studies have reported that moderate alcohol consumption is associated with a lesser prevalence of the metabolic syndrome (MetS). However, this relationship is still confusing and the presence of gene-environment interactions has been suggested. Our aim is to summarize evidence for gene-alcohol interactions in the MetS.

DATA SYNTHESIS

Research in gene-alcohol interactions applied to MetS is very complex due to the difficulties surrounding the definition of phenotype, environment and genotype, as well as in estimating the influence of the social context. In the MetS there is a constellation of metabolic disturbances the definition of which is still changing. Thus, most studies that have reported on gene-alcohol interactions have done so by analyzing isolated components. Likewise, the definition of alcohol consumption is also complex given that apart from the amount of ethanol consumed, the type of drink, the frequency of consumption, etc., may be important. No less difficult is the definition of genotype as there are many candidate genes involved, including not only those relevant for each phenotype studied, but also those related with alcohol metabolism, as well as those related to alcohol intake.

CONCLUSIONS

Although various studies exist that show statistically significant interactions between alcohol consumption and MetS components, a greater integration of variables as well as greater homogeneity in definitions is required.

Influencia de los factores genéticos y ambientales en el metabolismo lipídico y riesgo cardiovascular asociado al gen apoE

The apolipoprotein E (ApoE) plays an important role in lipid metabolism. This apoprotein presents three major isoforms (apoE2, apoE3 and apoE4) that modulate lipid levels. Carriers of the apoE4 allele have higher total and LDL-cholesterol plasma concentration and a greater coronary risk, particularly for myocardial infarction. Nevertheless, not all the people with this allele develop the disease, which suggests that other genetic or environmental factors are necessary for its total expression. In this review, we will analyze the importance of several polymorphisms in the apoE gene promoter region, as well as various environmental factors, including diet, in the association of this gene with lipid metabolism and cardiovascular risk.

The effect of the APOE polymorphism on HDL-C concentrations depends on the cholesterol ester transfer protein gene variation in a Southern European population

BACKGROUND

Apolipoprotein E (ApoE) locus has consistently shown a significant association with low-density lipoprotein cholesterol (LDL-C). However, its impact on high-density lipoprotein cholesterol (HDL-C) has been highly controversial suggesting that it may be context-dependent. We examined the gene-gene interaction between the common ApoE and the CETP polymorphisms in determining HDL-C concentrations in men and women from the general population.

METHODS

550 unrelated Caucasian subjects were randomly selected from a Mediterranean Region in Spain. Plasma lipids, anthropometric, clinical and lifestyle variables were measured. Common ApoE and CETP-TaqIB polymorphisms were determined.

RESULTS

We have found a gene-gene interaction between and ApoE and the CETP loci in determining HDL-C concentrations. Thus, after adjustment for gender, age, body mass index, tobacco smoking, alcohol consumption, physical exercise and medication, carriers of the E4 allele had lower HDL-C concentrations [mean and (standard error): 40.1 (2.6) mg/dL] than E2 subjects [47.7 (3.2) mg/dL; p=0.019], and even lower than those of the E3 subjects [44.7 (1.4) mg/dL; p=0.042], only if they had the B1B1 genotype. However, mean HDL-C concentrations were higher among those with E4 allele carrying the B2 allele at the CETP gene locus [50.5 (2.3) mg/dL], and lower among E2 subjects carrying the B2 allele [45.5 (2.6) mg/dL]. This interaction was observed in both men and women. This gene-gene interaction remained statistically significant even after additional adjustment for triglycerides.

CONCLUSIONS

The effect of the ApoE polymorphism on HDL-C concentrations depends on the CETP polymorphism, explaining some of the controversial results previously reported for this polymorphism.

Alcohol Use and Risk of Ischemic Stroke Among Older Adults

Background and Purpose— The association of light to moderate alcohol consumption with risk of ischemic stroke remains uncertain, as are the roles of potentially mediating factors and modification by apolipoprotein E (apoE) genotype.

Methods— We studied the prospective association of alcohol consumption and risk of ischemic stroke among 4410 participants free of cardiovascular disease at baseline in the Cardiovascular Health Study, a population-based cohort study of older adults from 4 US communities. Participants reported their consumption of alcoholic beverages yearly.

Results— During an average follow-up period of 9.2 years, 434 cases of incident ischemic stroke occurred. Compared with long-term abstainers, the multivariate relative risks of ischemic stroke were 0.85 (95% CI, 0.63 to 1.13), 0.75 (95% CI, 0.53 to 1.06), 0.82 (95% CI, 0.51 to 1.30), and 1.03 (95% CI, 0.68 to 1.57) among consumers of <1, 1 to 6, 7 to 13, and ≥14 drinks per week ( P quadratic trend 0.06). ApoE genotype appeared to modify the alcohol–ischemic stroke relationship ( P interaction 0.08), with generally lower risks among drinkers than abstainers in apoE4-negative participants but higher risks among drinkers than abstainers among apoE4-positive participants. We could not identify candidate mediators among lipid, inflammatory, and prothrombotic factors.

Conclusions— In this study of older adults, the association of alcohol use and risk of ischemic stroke was U-shaped, with modestly lower risk among consumers of 1 to 6 drinks per week. However, apoE genotype may modify this association, and even moderate alcohol intake may be associated with an increased risk of ischemic stroke among apoE4-positive older adults.